This video is of the automation process in action with me yammering on about all the various components that make it work:

From the Help File:
"This method for automagically creating skins in Assetto Corsa requires a few softwares and a little patience, and will probably feel a lot like watching a Rube Goldberg machine. This technique works well for iterating designs for small batches of skins or creating tens (or hundreds) at a time. I'm going to try my best to hit all the major points for getting this up and running. If you have specific questions about any particular piece you should be able to get answers with some quick googling or a post to the forum thread. The files included in this ZIP should work for creating Mazda MX5 Cup skins, but there will need to be some adjusting to replicate this automation to work with other cars. I'll provide screenshots as needed, and will hopefully remember to include helpful hints and describe relevant limitations/assumptions. Even if you don't run these scripts in their entirety they may spark some understanding or creativity in how you approach skin creation. "